Piston construction



June 18, 19-40. w. WUERFEL PISTON CONSTRUCTION Filed Feb. 23, 1937 Patented June 18, 1940 PATENT OFFICE PISTON CONSTRUCTION William Wuerfel, Philadelphia, Pa., assignor to Wilkening Manufacturing Company, Philadelphia, Pa., a corporation of Delaware Application February 23,119.37, Serial No. 127,093

'7 Claims.

The present invention relates to a new and useful piston and piston construction, the lower or skirt portion of which is split longitudinally and is resiliently expanded, so as to cause the skirt to expand radially, and also relates to a new and useful method or process of making pistons so as to impart resiliency to the skirt portions thereof The object of the present invention is to provide a split-skirt type piston, wherein the skirt is caused to expand outwardly against the cylinder wall by a generally uniform and predetermined force, so as to prevent the skirt from collapsing or fluttering at high piston speed, and sons to maintain the skirt in a generally round or circular formation.

With the above andother objects in view, which i will appear more fully from the following detailed description, the present invention consists in longitudinally slotting or splitting the skirt or lower portion of the piston, from its lowermost edge up to some point beneath the bottom ring-receiving groove, thenl slotting the, skirt also transversely to a suitable extent at the upper end orheacl end of the longitudinal slot or split, so as to permit a certain amount of expansion and contraction in the split portion of the skirt, providing suitable groovesin' the juxtaposed split edges of the skirt, and sopositioning a generally corrugated flat spring member in said groove, as to cause the same to exert a generally tangential force upon the two lonigtudinal split edges of said skirt, in

iopposite directions, so as to tend to expandsaid skirt.

a The present invention further consists of other novel details of construction, all as will more fully appear from the following detailed description.

For the purpose of illustrating the invention, there is shown in, the accompanying drawing forms thereof which are at present preferred, since the same have been found in practice to give satisfactory and reliable results, although it isto be understood that the various instrumenvtalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrange- Iment and organization of the instrumentalities as herein shown and described.

Referring to the drawing in which like reference characters indicate like parts:

Figure 1 represents a front elevational view of a piston embodying the present invention.

Figure 2 represents a bottom plan View of the same.

Figure 3 represents a plan view onan enlarged scale of the corrugated spring member taken on Figure 5 represents a section taken on line 5-5 of Figure 3. I

Figure 6 represents a perspective view ofthe corrugated spring member shown in Figure 1.

Figure '7 represents a front elevational view of an alternative corrugated spring member in its operative position. i

Figure 8 represents a front elevational view of another alternative corrugated spring member in its operative position.

Figure 9 represents a section taken on line 9-9 of Figure 8 on an enlarged scale.

Figure 10 represents a perspective view of the corrugated spring member illustrjated in Figure 8. l

The piston ll, of the present invention, may be of any suitable type and formed of any suit able metal, having any suitable number of ringreceiving grooves i2 and having a lower skirt portion I3, and wrist pin bearings land 15 formed integrally with the piston.

Intermediate the pair of wrist pin bearings l4 and IS, a relatively narrow parallel portion of the piston skirt l3 isremoved by any suitable cutter, or the piston may be formed initially with the slight gap or space It in the skirt l3. This leaves the skirtsplit along one generally longitool may include a shank portion adapted tobe a rotary 2 A gripped in any milling machine and cutter having opposite cutting edges. Thetool may be rotated at a suitable speed in the head of the milling machine and the cutting edge then fed through the slot Hi in a direction generally grooves 20 and 2| in the free edges of said slot. The expander spring 22 illustrated in Figures 1 to 6 inclusive is formed of any suitable fiat ribbon type spring metal of suitable thickness and isformed with generally similar corrugations 23.

all

t .45 parallel to the slot so as to form the opposed spring '22. Slight longitudinal projections 24 are provided along the front edge of the spring 22, and these projections cooperate with the slot grooves 2i] and 26 thus serving to lock the spring 5 22 in the slot it in a radial direction. These longitudinal projections 24 are preferably formed from and stamped out ofv the spring member 22 in such a direction asto cause them to extend beyond the crest or peak of each of the indi- 10 Vidual waves or corrugations 23. The spring 22 is locked in the slot it against lonigtudinal dis placement and prevented from sliding out of said slot by means of a transverse projection 25 which is formed integrally with and stamped out of the 15 upper end of the spring 22. The spring 22 is inserted in the slot 56 by merely slipping it in at the lower end thereof, then the front lonigtudinal projections 2d of the spring 22 are forced into the grooves 26 and 2i until the uppermost O spring projection 25 snaps into the "transverse slot I7. In this position, the lower edge of the upper spring projection 25- overhangs that portion of the lower surface of the upper transverse slot ll that is adjacent and abuts the upper extremity of the 'lonigtudinal slot it. When thus snapped in place, this spring 22 is effectively locked against longitudinal displacement, the reciprocation of the piston then having no effect "upo n the security of the spring in the piston.

3b The transverse overall dimension of the spring 22in its normal or unstressed condition (excluding its projections-2d) is greater than the normal distance between the juxtaposed edges i8 and 19 of the slot It by an extent sufficient to tension E5 the spring 22 when inserted in said slot 16 to the desired extent. 7

When the spring 22 is inserted between the "edges l8 and H) of the slot l6, the spring is tensioned transversely and exerts a tangential force generally equal to this tension. This tangential force exerted generally uniformly throughout the length of the slotted portion of the skirt l 3 causes this skirt to be expanded against the cylinder "wall so as to prevent the collapsing of the piston 4 skirt and to prevent the flutter of the piston skirt f at "high speeds.

-skirtunder all operating conditions.

In the modified form of the present invention illustrated in Figure '7, the upper transverse 5' 'spring projection 26 is formed or bent on the fsame side of the spring 22 as. is the adjoining {longitudinal spring projection 2%, as distinfguished from the-type shown in Figures 1 tot inclusive in which the upper transverse pro- ?5 jection'25 has been bent away from the spring 22 in a direction opposed to that in which its adjoining longitudinal projection'2 l has been bent. The particular direction in which the upper j'transverse spring projection may be bent is opfi tional, the important feature being that the underside of this projection should extend sufjfficie'ntly far beyond the body of the flat corrugated spring so as to contact a sufficient portion nf the lower side wall of the upper transverse 6 groove ll to retain the spring in the skirt slot "l 6 against longitudinal displacement.

In the other alternative embodimentof the present'invention illustrated in Figures 8, 9 and 10, a flat corrugated spring 22 is provided with a i series of alternately opposed projections 2i exftending along the radially outermost edge of the that spring member. These projections are equalllyfdistributedalong the longitudinal edge ofthe ffspr'ingand areso located with respect to the 7 75 "spring corrugations as to be disposed at the crest This also tends to expand the of each individual corrugation and are so formed as to project beyond said crest. These projections 2'! are preferably formed integrally with the corrugated spring. Thus, the spring member may originally be stamped out of any suitable 5 metal with the tongues 21 all extending beyond one edge of the spring and in the same plane as theater the spring body itself. These tongues or projections may then be alternatelybent in opposite directions so as to lie in a plane generally 10 perpendicular to the flat sides of the spring and this spring may then be corrugated in the manner shown in Figure 1G, or if desired the flat spring may first be corrugated and then these projections bent in opposite directions. It is important that this spring be so arranged that these projections 27 each project beyond the highest point of its associated individual corrugation. As illustrated in Figures 8 and 9, these projections 27 may then readily enter into the opposed grooves 29 and 2-! formed in the edges l8 and I9 of the longitudinal piston skirt slot Hi.

"In this particular embodiment of the present invent-ion, the upper end 28 of the spring 22 is extended slightly beyond the general outline of 25 the spring so as to cause said end 28 toproject into the transverse slot H to a suitable extent thereby locking the spring 22 in the grooves '20 and 2! and preventing it frornnsliding out. The spring. illustrated in Figures 8 to 10 inclusive may :30 be inserted into the longitudinal piston skirt slot l6by aligning the spring projections 21 with the slotpgrooves 20 and 2|, and then forcibly slipping the spring in said slot at the lower end thereof until the upper overhanging end 28 is snapped 3 into the transverse slot ll. In this position, the reciprocation of the piston does not effect the longitudinal security of the spring in said piston' In all the embodiments of the present invention illustrated in the drawing, the spring member 22 extends from the grooves 20 and 2! of the piston slot radially inwardly, and thus part of the spring 22 projects radially inwardly beyond the periphery of the inner piston wall, but no part of the spring 22 contacts the cylinder wall. 5

It is to be noted that in neither ofthe enibodiments illustrated do the longitudinal spring projections 24 or 27 extend suiiiciently far into the slot grooves 20 and 2| to contact the innermost surface thereof. As a result, the ex-l pansive force is exerted by the body of the spring contacting the slot edges l8 and I9, rather than by the spring projections 24 or 21 contacting the innermost groove surfaces.

The present invention may be embodied in other specific forms without departing from the spirit or essential. attributes thereof, and it is therefore desired that the present embodiment be-considered in all respects as illustrative and not restrictive, reference being had to the a r-i3 pended claims rather than to the foregoing description to indicate the scope of the invention.

Having thus described the invention, what is hereby claimed as new'and desired to be secured by Letters Patent is: 5

1. A. piston having a generally cylindrical skirt radially bounded by inner and outer generally cylindrical surfaces, said skirt being slotted gener ally longitudinally and having opposed parallel grooves in the juxtaposed'faces of said longitudinal slot intermediate said inner and outer generally cylindrical surfaces of said piston skirt,

and of a transverse width substantially less than the principal radial thickness of the major portion'of the skirt, the longitudinal slot in said skirt extending radially through the skirt wall so as to permit free radial movement of the skirt-portion on each side of the slot with respect to the skirt portion on the other side of the slot; and a corrugated ribbon-like spring member formed fromfiat spring metal operatively interposed between the two juxtaposed sides of said longitudinal slot with its convolutions extending generally tangenand of a transverse width substantially less than the principal radial thickness of the major portion of the skirt, the longitudinal slot in said skirt extending radially through the skirt wall so as to permit free radial movement of the skirt portion on each side of the slot with respect to the skirt portion on the other side of the slot; and a corrugated ribbon-like spring member formed from fiat springmetal operatively interposed between thetwo juxtaposed sides of said longitudinal slot with its convolutions extending generally tangentially of the skirt, tending to exert opposed tangential forces upon said skirt to expand the same, and in operative engagement with said grooves and with the median portions of said corrugated spring being radially un bounded and clear of the piston skirt wall.

3. A piston having the skirt portion thereof slotted generally longitudinally so as entirely to disconnect the two parts of the skirt on either side of the slot in the zone of the slot and so as i to permit the independent radial expansion and contraction of the skirt portions on either side of the slot, recessesformed in the juxtaposed sides of said longitudinal slot, a generally corrugated ribbon-like spring member formed from flat spring metal operatively interposed between the two juxtaposed sides of said generally longitudinal slot with its convolutions extending gen erally tangentially of the skirt, said spring member including means extending into and coacting with said recesses for retaining said spring member against generally radial displacement in relation to the piston skirt, and including means in interlocking engagement with said piston to retain said spring member against generally longitudinal displacement in relation to the piston skirt.

4. In a piston having a generally cylindrical skirt radially bounded by inner and outer generally cylindrical surfaces, said skirt being slotted generally longitudinally and having opposed parallel grooves in the juxtaposed faces of said longitudinal slot intermediate said inner and outer generally cylindrical surfaces of said piston skirt; said grooves being of a transverse width substantially less than the principal radial thickness of the major portion of the skirt; the longitudinal slot in said skirt extending radially through the skirt wall so as to permit free radial movement, of the skirt portion on each side of the slot with respect to the skirt portion on the other side of the slot, a generally corrugated ribbon-like spring member formed from flat spring metal and adapted to be operatively interposed between the two juxtaposed sides of said longitudinal slot to exert opposed tangential forces upon said skirt to expand the same, said spring member being adapted operatively to engage with said grooves and having its convolutions extending generally tangentially of said skirt.

5. In a piston having the skirt portion thereof slotted generally longitudinally so as to permit expansion and contraction of said skirt; and having the skirt wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portionof the skirt-wall, a generally corrugated ribbon-like spring formed from fiat spring metal and adapted to be operatively interposed between the juxtaposed edges of said slot and having its convolutions extending generally tangentially of the skirt to cause said skirt to expand by opposed tangential forces exerted by said spring; portions of the spring being adapted to interlock with portions of the piston for preventing radial displacement of the former with respect to the latter, and interlocking means for preventing the axial displacement of the spring with respect to the piston.

6. In a trunk type piston having a skirt slotted generally longitudinally and having a transverse slot communicating with the inner end of said longitudinal slot (that is, nearest the head-end of the piston) and having the skirt wall portions immediately marginal to said longitudinal slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt-wall, a generally corrugated ribbon-like spring member formed from fiat spring metal and adapted to be operatively interposed between the two juxtaposed edges of said longitudinal slot and having its convolutions extending generally tangentially of the skirt to exert opposed tangential forces upon the two opposed sides of said skirt on either side of said slot; portions of the spring member being adapted to interlock with portions of the piston for preventing radial displacement of the former with respect to the latter, and interlocking means for preventing the axial displacement of the spring member with respect to the piston.

7. In a piston having a skirt slotted generally longitudinally and having the skirt wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal piston skirt in a radial direction, without restraining the independent radial expansion and contraction of the skirt portions on opposite sides of the slot.

WILLIAM WUERFEL. 

